(a) The modulus of the wavelet bispectrum |BW| calculated for K=34 segments, 67% overlapping, with Tm=8 s, Ge=0.00001, using a fixed Morlet wavelet length of THF=20 s for calculation of the high frequencies. (b) A contour plot of the |BW|. For f2>0.9 Hz, the wavelet bispectrum is removed because the triplet (1 Hz, 1 Hz, 1 Hz) produces a high peak that is not physically significant. (c) The biphase 𝜙1 and (d) the biamplitude A1 for the bifrequency (1 Hz, 0.25 Hz)-peak 1, calculated using a 0.1 s time step.